CSC 216/001

1. CSC 216/001 Lecture 4

2. Unit Testing • Why is it called “unit” testing? • When should tests be written? • Before the code for a class is written. • After the code for a class is written, but before other classes are written. • After code for all classes is written, but before the classes are integrated. • After the classes are integrated.

3. Testing at the Boundaries • What does this mean? • Example (from the online notes): • For a method that removes an element from a list: • Test on a list with 1 element. • Test on a list that does not contain the element to be removed. • Test on a list where the element is at the beginning/end of the list. • Test on a list where the element appears multiple times. • Test on an empty list.

4. Testing a Square-Root Routine • From the text: What kinds of tests were proposed? • Test numbers greater than 1. • Test numbers less than 1. • Test negative numbers. • Test randomly generated numbers. • Apply the inverse of the square-root operation.

5. Testing a Stack • Suppose we have a Stack class implemented in an integer array. • Stack(int n); • void push(int i); • int pop(); • int top(); • What test cases should we use? (Discuss in groups.)

6. What is JUnit? • Regression testing framework • Written by Erich Gamma and Kent Beck • Used for unit testing in Java • Open Source • Released under IBM's CPL

7. Testing »Where Does JUnit Come From? • JUnit’s web site: http://junit.org/index.htm • Eclipse includes JUnit • Eclipse provides new GUI to run JUnit test cases and suites • JDT tools include a plug-in that integrates JUnit into the Java IDE • Allows you to define regression tests for your code and run them from the Java IDE.

8. Testing »JUnit Test Cases • JUnit Test Cases • Test case • Runs multiple tests • Implemented as subclass of TestCase • Define instance variables that store the state of the tests in the class • Initialize TestCase by overriding setUp method • Cleanup after test case is done by overriding tearDown method • The Test framework will invoke the setUp and tearDown methods.

9. Testing »Creating JUnit Test Cases in Eclipse • Create a new package to contain your test case classes. • Add the JUnit JAR file to the project’s buildpath.

10. Testing »Creating JUnit Test Cases in Eclipse • Select your testing package • From the context menu select New » JUnit Test Case. This opens the New JUnit Test Case Wizard. • Fill in the name of your test case in the Name field. • Select the method stubs that you want Eclipse to generate • This will create the corresponding class in your testing package

11. Testing »JUnit TestCase Template public class NewTestCase extends TestCase { public static void main(String[] args) { } public NewTestCase(String arg0) { super(arg0); } protected void setUp() throws Exception { super.setUp(); } protected void tearDown() throws Exception { super.tearDown(); } }

12. Testing »Adding Tests to Test Cases • Any method in a TestCase class is considered a test if it begins with the word “test”. • You can write many tests (have many test methods) • Each test method should use a variety of assert… methods to perform tests on the state of its class. • Assert methods are inherited

13. Testing »JUnit Assert Methods • Assert methods include: • assertEquals(x,y) • assertFalse(boolean) • assertTrue(boolean) • assertNull(object) • assertNotNull(object) • assertSame(firstObject, secondObject) • assertNotSame(firstObject, secondObject)

14. Testing »Adding Two Tests to JUnit Test Case public class NewTestCase extends TestCase { public static void main(String[] args) { } public NewTestCase(String arg0) { super(arg0); } protected void setUp() throws Exception { super.setUp(); } protected void tearDown() throws Exception { super.tearDown(); } public void testCompareSucceed() { assertEquals(0, 0); //this assertion will succeed } public void testCompareFail() { assertEquals(0, 1); //this assertion will fail } }

15. Testing »Running JUnit Test Case • Select TestCase class • From the Run menu select Run » Run As » JUnit Test • This will run the tests in your TestCase class along with the setUp and tearDown methods • You will then get a report in the JUnit window

16. Testing »JUnit Window • Red indicates a test has failed • You can see which test failed • You can see the call trace leading to the failure • If you wish to see the tests in TestCase click on the Hierarchy tab

17. Testing »JUnit Window • You can see how many tests ran • How many failures occurred • You can see the details of the failure • Errors occur when exceptions are thrown (e.g., when assertions fail)